Hydrogen for fuel cells can be produced by means of fuel processing. In a fuel processor, a hydrocarbonaceous fuel is converted into a hydrogen-rich gas stream that can be used in a fuel cell for the generation of electricity.
Typically in a fuel processor, the hydrocarbonaceous fuel is first reacted with oxygen and/or steam by means of catalytic partial oxidation, autothermal reforming, steam reforming or a combination of one or more thereof to obtain a gas mixture comprising carbon oxides and hydrogen. The thus-obtained gas mixture is subsequently reacted with steam over a water-gas shift conversion catalyst to convert carbon monoxide into carbon dioxide with concurrent production of hydrogen. A gaseous stream comprising hydrogen and carbon dioxide is thus obtained. This stream may be fed to a fuel cell, optionally after purification.
Fuel processors that integrate steam reforming of hydrocarbonaceous streams with selective hydrogen removal are also described in the art, for example in WO 02/070402, U.S. Pat. No. 5,938,800, U.S. Pat. No. 6,348,278, US 2006/0013762 and U.S. Pat. No. 5,861,137. Such integrated steam reforming/hydrogen separation devices operate at lower temperatures than conventional steam reforming reactors and are not limited by normal equilibrium limitations. In such integrated devices, hydrocarbons are reformed to carbon dioxide and hydrogen according to (in the case of methane):CH4+2H2→CO2+4H2 
Advantages of such integrated steam reformer/hydrogen removal devices as compared to fuel processors without integrated hydrogen removal are that no separate reaction zone for the water-gas shift conversion is needed and that a substantially pure stream of hydrogen and a separate stream comprising carbon dioxide are obtained.
In WO 02/070402 is disclosed a process and apparatus for steam reforming of a vaporizable hydrocarbon to produce H2 and CO2, using a membrane steam reforming reactor and flame-less distributed combustor. A hydrogen selective separation membrane is provided to remove the produced hydrogen from the reaction. The flame-less distributed combustor provides the heat to drive the steam reforming reaction. It is mentioned in WO 02/070402 that part of the produced hydrogen can be directed to the flame-less distributed combustor. Disadvantage of the process and apparatus of WO 02/070402 is that it requires the use of an additional separate flame-less distributed combustor. Furthermore, the thickness of the catalyst layer between the flame-less distributed combustor and the membrane is restricted due to heat transfer limitations.
In US 2006/0013762, a process for the production of hydrogen and carbon dioxide from hydrocarbons is disclosed. This process involves supplying a gaseous stream of hydrocarbons and a molecular oxygen-containing gas, e.g. air, oxygen enriched air or pure oxygen, to a first reaction zone containing a partial oxidation catalyst and catalytically partially oxidizing the hydrocarbons in the gaseous stream. The effluent of the first reaction zone is supplied together with a second gaseous stream of hydrocarbons and steam to a second reaction zone containing a steam reforming catalyst wherein the hydrocarbons are catalytically reformed. The heat required for the second steam reforming reaction is supplied by the effluent from the first reaction zone. In the second reaction zone hydrogen is separated from the reformed gas by a selective membrane and a gaseous stream rich in carbon dioxide is obtained.
In U.S. Pat. No. 5,861,137 is described a steam reformer comprising a fixed bed of steam reforming catalyst surrounding at least part of a hydrogen-permeable, hydrogen-selective membrane and a fixed bed of catalytic combustion catalyst arranged around at least part of the fixed bed of steam reforming catalyst. The steam reforming bed is heated by the heat generated by the catalytic combustion of reforming by-product gases and optionally part of the produced hydrogen with air.
In the integrated steam reforming/hydrogen removal process of the prior art, a substantially pure stream of hydrogen is obtained together with a CO2 comprising gas stream. The CO2 comprising gas stream is diluted with nitrogen unless substantially pure oxygen is used as the source of oxygen instead of air. However, pure oxygen is difficult and expensive to produce. Furthermore, the use of pure or even concentrated oxygen poses a practical hazard.